The present invention relates to a method of displaying ultrasonic images and apparatus for ultrasonic diagnosis, and particularly to a method of displaying ultrasonic images and apparatus for ultrasonic diagnosis with the enhanced ability of depicting small blood vessels in Doppler power mode.
FIG. 9 is a block diagram showing a conventional apparatus for ultrasonic diagnosis. The ultrasonic diagnostic apparatus 500 includes a ultrasonic probe 1 and ultrasonic wave transmitter/receiver 2, by which multiple ultrasonic pulses are transmitted at a certain time interval and ultrasonic echo signals from multiple observation points in depth direction on multiple ultrasonic beam lines are received.
In Doppler power mode, the ultrasonic echo signals are fed to an orthogonal detector 4. The orthogonal detector 4 includes mixers 4a and 4b, by which the ultrasonic echo signals are multiplied to reference signals provided by reference signal generators 4c and 4d, and it produces an orthogonal component Q and in-phase component I at the outputs of low-pass filters (LPFs) 4h and 4i. A/D converters 5 and 6 render the A/D conversion for the orthogonal component Q and in-phase component I, and store the resulting data in memories 7 and 8.
Moving target indication (MTI) filters 9 and 10 read the orthogonal component Q and in-phase component I out of the memories 7 and 8, and remove unneedful clutter components (Doppler components from such tissues as the wall of heat having a relatively slow movement) from these components Q and I. An autocorrelation calculator 11 calculates power data P(R,.phi.) (where R represents the depth of observation point and .phi. represents the beam line number) from the orthogonal component Q and in-phase component I that have been rid of the unneedful components.
A digital scan converter (DSC) 13 converts the power data P(R,.phi.) into pixel values and implements the two-dimensional mapping for the pixel values based on the positions of observation points, thereby yielding image data DI. A CRT display unit 14 displays a ultrasonic image of Doppler power mode derived from the image data DI.
FIG. 10 shows an example of ultrasonic images of Doppler power mode. Displayed in this example over the background H, which is generally black, are blood vessels P1 and P2 in the orange color and at various luminance levels depending on the magnitude of the power.
Returning to FIG. 9, in color flow mapping (CFM) mode, the autocorrelation calculator 11 implements the calculation of autocorrelation between ultrasonic pulses for the orthogonal component Q and in-phase component I, thereby producing velocity data v(R,.phi.). The DSC 13 converts the velocity data v(R,.phi.) into pixel values, implements the two-dimensional mapping for the pixel values based on the positions of observation points, thereby yielding image data DI.
The CRT display unit 14 displays a ultrasonic image of CFM mode derived from the image data DI. For ultrasonic images of CFM mode, the background is generally black, and blood vessels are displayed in red and blue and at various luminance levels depending on the blood flow velocity and direction.
In B mode, the ultrasonic echo signals are fed to a B-mode processor 3. The B-mode processor 3 produces B-mode data from the magnitude of ultrasonic echo signals and delivers the resulting data to the DSC 13. The DSC 13 converts the B-mode data into pixel values and implements the two-dimensional mapping for the pixel values based on the positions of observation points, thereby yielding image data DI.
The CRT display unit 14 displays a ultrasonic image of B mode derived from the image data DI. For ultrasonic images of B mode, the background is generally black, and tissues are displayed in achromatic colors of various luminance levels depending on the magnitude of the ultrasonic echo signals.
However, the conventional ultrasonic diagnostic apparatus 500, which produces ultrasonic images of Doppler power mode as shown in FIG. 10, is not capable of showing clearly the border between the blood vessel images P1 and P2 and the background H, and therefore it is difficult for the viewer to identify small blood vessels accurately.